I would first ask if she uses Charmin, that damn paper sticks everywhere.
But in all seriousness, it really depends on the level of the relationship:
1. If it's a one night stand flick it, spit ball it, who cares just loose it and carry on with the muff diving.
2. if it's an ongoing relationship, make a non-cruel joke (the charmin one above should be as far as you take it).
